Verifying Security Properties in Unbounded Multiagent Systems

We study the problem of analysing the security for an unbounded number of concurrent sessions of a cryptographic protocol. Our formal model accounts for an arbitrary number of agents involved in a protocol-exchange which is subverted by a Dolev-Yao attacker. We define the parameterised model checking problem with respect to security requirements expressed in temporal-epistemic logics. We formulate sufficient conditions for solving this problem, by analysing several finite models of the system. We primarily explore authentication and key-establishment as part of a larger class of protocols and security requirements amenable to our methodology. We introduce a tool implementing the technique, and we validate it by verifying the NSPK and ASRPC protocols

Refinement of Kripke Models for Dynamics

We propose a property-preserving refinement/abstraction theory for Kripke Modal Labelled Transition Systems incorporating not only state mapping but also label and proposition lumping, in order to have a compact but informative abstraction. We develop a 3-valued version of Public Announcement Logic (PAL) which has a dynamic operator that changes the model in the spirit of public broadcasting. We prove that the refinement relation on static models assures us to safely reason about any dynamic properties in terms of PAL-formulas on the abstraction of a model. The theory is in particular interesting and applicable for an epistemic setting as the example of the Muddy Children puzzle shows, especially in the view of the growing interest for epistemic modelling and (automatic) verification of communication protocols

Model Checking Detectability of Attacks in Multiagent Systems

Information security is vital to many multiagent system applications. In this paper we formalise the notion of detectability of attacks in a MAS setting and analyse its applicability. We introduce a taxonomy of detectability specifications expressed in temporal-epistemic logic. We illustrate the practical relevance of attack detectability in a case study applied to a variant of Kerberos protocol. We model-check attack detectability in automatically generated MAS models for security protocols

Model Checking Security Protocols: A Multiagent System Approach

Security protocols specify the communication required to achieve security objectives, e.g., data-privacy. Such protocols are used in electronic media: e-commerce, e-banking, e-voting, etc. Formal verification is used to discover protocol-design flaws. In this thesis, we use a multiagent systems approach built on temporal-epistemic logic to model and analyse a bounded number of concurrent sessions of authentication and key-establishment protocols executing in a Dolev-Yao environment. We increase the expressiveness of classical, trace-based frameworks by mapping each protocol requirement into a hierarchy of temporal-epistemic formulae. To automate our methodology, we design and implement a tool called PD2IS. From a high-level protocol description, PD2IS produces our protocol model and the temporal-epistemic specifications of the protocol’s goals. This output is verified with the model checker MCMAS. We benchmark our methodology on various protocols drawn from standard repositories. We extend our approach to formalise protocols described by equations of cryptographic primitives. The core of this extension is an indistinguishability relation to accommodate the underlying protocol equations. Based on this relation, we introduce a knowledge modality and an algorithm to model check multiagent systems against it. These techniques are applied to verify e-voting protocols. Furthermore, we develop our methodology towards intrusion-detection techniques. We introduce the concept of detectability, i.e., the ability of protocol participants to detect jointly that the protocol is being attacked. We extend our formalisms and PD2IS to support detectability analysis. We model check several attack-prone protocols against their detectability specifications

Model checking security protocols : a multiagent system approach

Security protocols specify the communication required to achieve security objectives, e.g., data-privacy. Such protocols are used in electronic media: e-commerce, e-banking, e-voting, etc. Formal verification is used to discover protocol-design flaws. In this thesis, we use a multiagent systems approach built on temporal-epistemic logic to model and analyse a bounded number of concurrent sessions of authentication and key-establishment protocols executing in a Dolev-Yao environment. We increase the expressiveness of classical, trace-based frameworks by mapping each protocol requirement into a hierarchy of temporal-epistemic formulae. To automate our methodology, we design and implement a tool called PD2IS. From a high-level protocol description, PD2IS produces our protocol model and the temporal-epistemic specifications of the protocol’s goals. This output is verified with the model checker MCMAS. We benchmark our methodology on various protocols drawn from standard repositories. We extend our approach to formalise protocols described by equations of cryptographic primitives. The core of this extension is an indistinguishability relation to accommodate the underlying protocol equations. Based on this relation, we introduce a knowledge modality and an algorithm to model check multiagent systems against it. These techniques are applied to verify e-voting protocols. Furthermore, we develop our methodology towards intrusion-detection techniques. We introduce the concept of detectability, i.e., the ability of protocol participants to detect jointly that the protocol is being attacked. We extend our formalisms and PD2IS to support detectability analysis. We model check several attack-prone protocols against their detectability specifications